Dynamically Monitoring Vocal Fatigue and Recovery Using Aerodynamic, Acoustic, and Subjective Self-Rating Measurements

Objectives. This study aimed to quantify the effects of vocal loading and vocal rest using aerodynamic, acoustic, and self-rating measurements. Methods. Ten participants were recruited to perform vocal loading tasks lasting 60 minutes, followed by 30 minutes of vocal rest. Objective parameters (phonation threshold pressure, fundamental frequency, jitter, shimmer, and noise-to-harmonics ratio) and subjective parameters (current speaking effort level and laryngeal discomfort) were taken at different time intervals: before vocal loading (baseline), after 15 minutes (L15), 30 minutes (L30), 45 minutes (L45), and 60 minutes (L60) of vocal loading, as well as after 5 minutes (R5), 10 minutes (R10), 20 minutes (R20), and 30 minutes (R30) of vocal rest. Results. Phonation threshold pressure was found to increase significantly within the first 15 minutes of the vocal loading task (P = 0.032), followed by a relatively gentle increase in the subsequent 45 minutes. Subjective self-ratings increased significantly after 30 minutes of loud reading (P< 0.05). Phonation threshold pressure recovered faster than subjective parameters after the vocal loading activity had finished. Fundamental frequency was found to consistently increase during vocal loading but return to baseline rapidly within 5 minutes of vocal rest. However, no significant changes in jitter, shimmer, and noise-to-harmonics ratio were observed after vocal loading. Conclusions. Phonation threshold pressure and self-ratings may have the potential to track vocal fatigue and recovery. Furthermore, a dynamic monitor of vocal fatigue was presented, which may further provide a guide for appropriate voice use.